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Unformatted text preview: 149 149 CHAPTER 7 Transistor Circuits 150 Chapter 7: Transistor Circuits CHAPTER 7: PROBLEMS 7.1 Consider the circuit shown below. For the transistors, assume that V BEON = 0.7V, V CESAT = 0.2V and = 100. (a) Find the current flowing through the 100 resistor when V o = 3v as shown. (b) Using your result from part (a), find I B1 , I C1 , I C2 , and the value of V i for this circuit which leads to V o = 3v. 7.2 Consider the circuit shown below. For the transistor, assume that V BEON = 0.7V, V CESAT = 0.2V and = 100, and for the diode, assume that V DON = 0.7V. +- V CC = 10V 100k 100 V o = 3v Q1 Q2 V i +- V CC = 15V V i V o 10k 1k 151 151 Analog Electronics (a) Find the range for V i that keep the transistor in the CUTOFF region. What region is the diode in? (b) Find the range for V i that leaves the transistor in the FOR- WARD-ACTIVE region. What region will the diode be in? (c) Find the range for V i that keep the transistor in the SATU- RATION region. What region is the diode in? 7.3 For the transistor below, assume that V BEON = 0.7V, V CESAT = 0.2V and = 100. (a) Calculate the value of the voltage V x , the value of the base current I b and the output value V o of the circuit. Make sure to justify your assumption about which region the transistor is in. (b) If R L is changed to 1k what region will the transistor be in? Justify your answer. V CC = 10V 1k 1k 10k R L =10k 10k V x V o I b 152 Chapter 7: Transistor Circuits 7.4 Consider the circuit shown below. For the transistors, assume that V BEON = 0.7V, V CESAT = 0.2V and = 100, and for the Zener diode, assume that V DON = 0.7V and V Z = -5.7V. Find the voltages at nodes A, B, C and D. Make sure to justify your assumptions about the modes of the transistors and the diode. 7.5 For the circuit shown below, plot I L vs. V i for the range of 0v to 10v. Make sure to use units and note any breakpoints on the graph. You may assume that V BEON = 0.7V, V CESAT = 0.2V and = 100. +- 10v Q1 Q2 D A B C +- V CC = 10V V i 100k 100k 20k I L 20k 153 153 Analog Electronics 7.6 For the circuit shown below, plot V o vs. V i for the range of 0v to 5v. Make sure to use units and note any breakpoints on the graph. You may assume that V BEON = 0.7V, V CESAT = 0.2V and = 100 for both transistors....
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